1. Field of the Invention
The invention pertains to the field of internal combustion engine exhaust handling and filtration. More particularly, the invention pertains to a system for the filtration of particulate matter contained in the exhaust gas of diesel engines, including means for monitoring filter backpressure, controlling and by-passing or activating said filtration system automatically and/or on demand.
2. Description of Related Art
Diesel engine exhaust gas contains considerable amounts of exhaust particulates. Various kinds of filters or trapping devices have been employed for removing such particulates. However, a typical diesel engine may emit on the order of a gallon of particulate in 1,000 miles of continuous operation. After a sufficient amount of particulate has been trapped, the resultant backpressure adversely affects the operation of the engine. Vehicles that utilize filter elements for trapping exhaust particulates must therefore employ means for dealing with this problem.
There have been proposed a number of diesel exhaust gas cleaning devices, which include filter regeneration means. For example, disclosed in U.S. Pat. Nos. 4,450,681, 4,485,621 and 4,538,412 are filter regeneration systems comprising various means for igniting and burning the trapped exhaust particulates. Such regeneration systems conventionally include valve means for by-passing at least a portion of the exhaust gas during at least a portion of the regeneration cycle. However, such regeneration techniques generally have been subject to one or more of the following disadvantages, which have precluded the commercial acceptance thereof: (1) an inability of the filter element to undergo regeneration so as to maintain effectiveness over long periods, (2) regeneration can reduce the efficiency of the filter element, (3) regeneration can damage the filter element such as by the generation of corrosive gases, and (4) regeneration can produce excessive amounts of harmful by-products such as sulfates.
U.S. Pat. No. 5,154,894 discloses a catalytic converter for use in the exhaust system of an internal combustion engine, having a rigid outer canister with a catalyst support disposed therein for movement between a first position adjacent in inlet end of the canister and a second position located in spaced relationship with said inlet end. In its first position, the substrate seals the inlet thereby forcing the entire exhaust flow through the fluid flow passages within the catalyst support, which are in axial alignment with the converter inlet. The effect of forcing the totality of flow reduced volume of the substrate to the entire thermal energy of the exhaust stream thereby assisting in a reduction in the catalyst light-off time. Following catalyst light-off, the catalyst support is moved to its second, spaced position in which the entire frontal area of the converter is exposed to the exhaust flow thereby lowering backpressure of the converter and preventing converter over-temperature problems.
U.S. Pat. No. 5,123,243 discloses a method and apparatus for removing solid particulate matter from the exhaust of a diesel engine, which comprises passing the engine's exhaust flow through at least a part of filter means to trap solid particulate matter contained initially in the exhaust, thereby to remove said matter from said exhaust flow, interrupting the exhaust flow through at least said part of the filter means, at a time when the preceding period of exhaust flow therethrough is of sufficiently brief duration that the trapped particulate matter has not become resistant to subsequent combustion in the engine, during said interruption back-flushing at least said part of the filter means thereby to dislodge from the filter means, and entrain, said solid particulate matter for the purpose of removing it from the filter means, and transporting said dislodged solid particulate matter to the intake of said engine, so that said matter can be combusted in the engine.
U.S. Pat. No. 5,024,054 discloses a diesel engine exhaust system including a plurality of valved ceramic filters connected in parallel in the exhaust stream and loaded sequentially. While one filter is preferentially loaded, a second filter is opened to the exhaust stream, when backpressure reaches a predetermined value. The secondary filter is removed from the exhaust stream when air flow to the engine drops a discrete amount below a peak air flow, determined by the backpressure, which would cause the secondary filter to be placed in the exhaust stream. The preferentially loaded filter is bypassed when completely loaded and regenerated. The secondary filter is then preferentially loaded and the sequence continues.
U.S. Pat. No. 5,009,065 discloses an exhaust processor for filtering particulate matter from a combustion product. The exhaust processor includes a partition situated inside a housing to form a first flow passage and a second flow passage in an upstream portion of the housing. A main substrate is mounted in the first flow passage for solid particle filtration. An auxiliary substrate is situated in the second flow passage to filter combustion product passing through the second flow passage during regeneration of the main substrate. A muffler is situated in a downstream portion of the housing and is arranged so that the entire spatial volume of the muffler can be utilized by combustion product passing through either the first or second flow passage.
U.S. Pat. No. 4,538,412 discloses an exhaust particulate cleaning device for a diesel engine, comprising a trap case, which is located in a passageway of the exhaust gas and which has therein a filter material for trapping the exhaust particulates contained in the exhaust gas, an electric heater for igniting and burning the exhaust particulates trapped in the filter material, a larger bypass passage of the exhaust gas bypassing the trap case, and a control valve in the bypass passage for opening and closing the bypass passage.
U.S. Pat. No. 4,503,672 discloses an exhaust cleaner system for use in the exhaust system of a diesel engine with a particulate filter positioned in a trap housing with an exhaust inlet thereto and an exhaust outlet therefrom. A pair of exhaust ducts are positioned in the inlet end of the exhaust outlet whereby to define, in effect, three separate exhaust flow zones through the filter and a flow limiter valve is operatively positioned to sequentially control flow through the exhaust ducts. Glow plugs are located so as to extend into the zones of the filter associated with the exhaust ducts to initiate incineration of particulates during reduced exhaust flow conditions as controlled by the flow limiter valve.
U.S. Pat. No. 4,485,621 discloses a method for removing particulates from internal combustion exhaust gases in a system, which includes a first gas conduit which connects with an engine exhaust pipe and which communicates with a trapping chamber containing means for filtering or trapping particulate matter present in the exhaust gas. A second gas conduit connects with said first gas conduit at a location upstream of the said trapping chamber and leads to a regenerating chamber which contains an electrically conductive substrate which carries an oxidation catalyst. A third gas conduit carries the hot gas from the regenerating chamber and connects with said first gas conduit at a location also upstream of said trapping chamber. The electrically conductive substrate material within the regenerating chamber is part of an electrical circuit and is heated by current passing therethrough. Means are provided for injecting a combustible fuel into the regenerating chamber wherein the fuel-exhaust gas mixture is effectively heated and burned therein and the heated gas then passes into the trapping chamber to incinerate and burn off the particulate collected therein. Valve means are provided to selectively direct exhaust gas flow through to the trapping chamber and the regenerating chamber.
U.S. Pat. No. 4,450,681 discloses a carbon particulates cleaning device, comprising a carbon particulate catching means, a fuel injecting means, a fuel retaining means for retaining the fuel injected by the fuel injecting means near the carbon particulates catching means, a fuel igniting means for igniting the fuel retained by the fuel retaining means, and a gas blowing means which blows gas for maintaining the fuel burning and applying the heat of the burning fuel into the carbon particulates caught by the catching means. The carbon particulates caught by the carbon particulates catching means are effectively burnt and eliminated by supplying gas which is heated due to the burning heat of the fuel ignited by the fuel igniting means.
U.S. Pat. No. 3,972,184 discloses an exhaust system for an internal combustion engine including a catalytic converter. A valve-controlled by-pass around the catalyst bed in the converter is provided, such that the exhaust gas is only passed through the catalyst bed during engine warm-up. The valve is automatically controlled by engine temperature such that after the engine attains operating temperature the by-pass valve opens and the exhaust gas by-passes all catalyst.
U.S. Pat. No. 4,803,838 discloses a device for removing particulates from the exhaust gas of a vehicle internal combustion engine during those times that the emission of such particulates into the atmosphere would be of greatest danger to persons in the vicinity of the vehicle. The system comprises valve means connected to the vehicle exhaust manifold for normally directing exhaust to the atmosphere when in the non-activated condition. The valve means directs exhaust to a particulate filter when in the activated condition. Means responsive to the starting of the engine activates the valve means for a predetermined period of time. The valve means can also be activated by shifting into reverse gear.
However, the device of U.S. Pat. No. 4,803,838 is known to accumulate particulates, in a relatively short time, sufficient to produce enough backpressure to cause its control system to activate the backpressure warning light, indicating that the filter requires service. Thus, this system is prone to false indications that the filter requires service, inducing costly maintenance procedures to be performed unnecessarily. Similarly, an improved version of the system of U.S. Pat. No. 4,803,838 also is known to accumulate particulates, in a relatively short time, sufficient to produce enough backpressure to cause its control system to by-pass the filter (temporarily or intermittently), particularly depending on throttle position, vibration and other factors, thus producing unwanted soot and/or false indications that the filter requires service. Another problem is that, when the backpressure reaches a level sufficient to activate the system, the backpressure warning light in this system merely blinks several times and then goes dark. Because the warning light does not remain lit, vehicle operators frequently forget that the filter requires service.
U.S. Pub. No. 20030135323A1 discloses a method and device for operating an engine of a motor vehicle. Driving condition parameters of the engine and/or the motor vehicle are collected over a predetermined period of time. The probabilities of parameters for the future operation of the engine in relation to the captured driving condition parameters are ascertained, and operating parameters of the engine are adjusted in relation to the ascertained probability values for the parameters. Preferably, navigation signals are read in by external navigator systems, such as GPS systems, to additionally determine the geographical position of the motor vehicle.
The foregoing methods and apparatus for internal combustion engine exhaust handling and filtration generally suffer from numerous problems and limitations. For example, many are inefficient or even ineffective over long periods, or develop backpressure that negatively affects engine performance, while others do not adequately filter the exhaust gasses, particularly when needed to protect the health of individuals located nearby. More particularly, the system described in U.S. Pat. No. 4,803,838 suffers from the problem that, when the filter begins to accumulate particles, the resulting backpressure causes the backpressure warning light to turn on and off intermittently, thus giving false indications of the state of the filter. Even when operating properly, the backpressure warning light merely blinks several times, when activated, and then it goes dark. This results in neglect and less frequent filter maintenance than is desired for efficient operation of the filter system.
Thus there is a need in the art for an exhaust particulate removal system that overcomes the disadvantages of the prior art. More particularly, there is a need for an improved exhaust particulate removal control system that is less prone to false indications that the filter requires service, less likely to produce unwanted soot due to by-passing the filter unnecessarily, and more reliable generally.